The benefits of continuously redirecting the airflow of an electrical fan are well known. Numerous fans intended to cool persons have been equipped with redirection mechanisms over the years since electrical fans were initially developed.
Rectangular fans, generically known as "box" fans, have often been equipped with rotating circular front grills which include airstream deflectors that are pitched from the fan's general direction. As air leaves the fan blade within the fan, it travels forward until it reaches the front grill deflectors and is thereby redirected at some angle. As the front grill rotates, the redirection angle is changed such that the airstream follows a basically conical shape. Rotation of the front grill is accomplished most often by direct coupling to an independent low-speed motor. Alternately, the front grill is often rotationally uncoupled and driven by the forces of the airstream. In the former case, the independent motor adds expense to the manufacture and use of the fan. In the later case, the energy taken from the airstream to rotate the grill reduces the total energy of the airstream, resulting in a slower airstream velocity and shorter downstream air penetration. In either case, the airflow pattern from the fan describes only a circular pattern, in accordance with the circular rotation of the grill.
Another class of fans, generically known as "oscillating" fans, employ various mechanisms to continuously change the airstream's general direction. Both the motor and blade of the fan are continually repositioned by the mechanisms. Some of these employ independent low speed motors to cyclically swivel the fan back and forth in a particular pattern. Some derive their oscillating energy from the airstream. In either case, the drawbacks previously mentioned apply.
A very common oscillating fan design is depicted in FIGS. 1 through 2(c) and employs an output shaft (M4) extending from both the front and the back of the motor (M). At the downstream end (M5) of the shaft is attached the fan blade (F1). The upstream end of the shaft includes a worm gear (not shown). A reducing gearbox (B) is coupled to the worm gear and includes a low-speed output shaft (B1), positioned perpendicularly to the fan's output shaft, and pivotably connected to mechanical ground (B4) by and a planar hinged link member (B2/B3). The fan head (H), including the motor and blade, are free to pivot relative to mechanical ground about a single axis (M2) which is perpendicular to the fan's output shaft and to the gearbox's output shaft. Rotation of the fan's output shaft causes rotation of the low speed shaft which in turn, by opening and closing of the hinged link, causes planar pivoting of the fan head back and forth about the single axis. FIGS. 2(a), 2(b), and 2(c), are partial top views showing the configurations of the hinged link member while the fan head (not shown) is directed in various positions.
In FIG. 2(a), with low-speed output shaft (B1), and therefore also hinged link member portion (B2), positioned clockwise ninety angular degrees from single axis (M2), as shown in solid line representation, the fan head is directed forwardly. In the phantom line representation of FIG. 2(a), with low-speed output shaft (B1), and therefore also hinged link member portion (B2), positioned zero angular degrees from single axis (M2), the fan head is directed rightward.
In FIG. 2(b), with low-speed output shaft (B1), and therefore also hinged link member portion (B2), positioned counter-clockwise ninety angular degrees from single axis (M2), as shown in solid line representation, the fan head is directed leftward. In the phantom line representation of FIG. 2(b), with low-speed output shaft (B1), and therefore also hinged link member portion (B2), positioned one hundred eighty angular degrees from mechanical ground connection (B4), the fan head is directed farther leftward. This condition represents the farthest leftward direction obtained by this system.
In FIG. 2(c), with low-speed output shaft (B1), and therefore also hinged link member portion (B2), positioned clockwise approximately one hundred fifty angular degrees from single axis (M2), as shown in solid line representation, the fan head is directed leftward. In the phantom line representation of FIG. 2(c), with low-speed output shaft (B1), and therefore also hinged link member portion (B2), positioned clockwise ninety angular degrees from single axis (M2), as in the solid line representation of FIG. 2(a), the fan head is directed forward.
Although the oscillation mechanism of the prior art depicted in FIGS. 1 through 2(c) has proven reliable, economical, and more effective in broadcasting the airstream over a wider area than non-oscillating fans, it suffers from it's inability to direct the airstream from the plane on which it pivots.
Some fans of the prior art employ the basic concept of the previous design, but instead include a low speed gearbox output shaft which extends parallel with the fan's output shaft. This low speed shaft is rotatably linked by a single rigid link member to mechanical ground. The fan head is free to pivot relative to mechanical ground about two axes which are perpendicular to each other and to the fan's output shaft. Rotation of the fan's output shaft causes rotation of the low speed shaft which in turn causes gyration of the fan about the two axes in a circo-conical pattern. Although this mechanism has also proven reliable, economical, and more effective in broadcasting the airstream over a wider area than non-oscillating fans, it suffers from it's inability to direct the airstream from said circo-conical pattern.
Prior fans have been known which employ mechanisms that convert rotation of the fan motor into continuous circo-conical redirection of the airstream. However, these fans do not employ means to manage the abnormal forces encountered as a result of the vertical movement of the fan head with and against gravity. Nor do these fans employ means to avoid looseness within the mechanism as the mechanism wears because of these abnormal conditions.